Propeller tip centrifugal pitch control



March 16, 1937. J, H. AC BS 2,074,149

PROPELLER TIP CENTBIFUGAL PITCH CONTROL Filed May 2'7, 1936 Patented Mar. 16, 1937 UNITED STATES PATENT. OFFICE PRQPELLER TIP CENTRIFUGAL PITCH CONTROL Joseph Jacobs, Minneapolis, Minn. Application May 27, 1936, Serial No. 82,023

3 Claims. (01.170-162) An object of my invention is to provide a prol peller capable of substantially the same results as the usual variable pitch propeller but of such nature that an ordinary. hub such as employed innon-variable propellers-may be used.

A more specific object is to provide such a 15 propeller wherein the main portion of the blade is fixed in pitch and only the tip portion is variable in pitch.

Another object is to provide such a propeller wherein the tip portion is automatically varied 20 in pitch responsive to variation in the speed of rotation of the propeller.

A further object is to provide such a propeller of simple, light, compact, reliable and inexpensive construction.

25 These and other objects will be more apparent from the following description made in connection with the accompanying drawing wherein like reference characters refer to similar parts throughout the several views, and in which:

30 Fig. 1 is a f ont view of a propeller comprising an embodiment of my invention;

Fig. 2 is a partially broken away front view of the outer portion of a blade of the propeller of Fig. I;

Fig. 3 is a cross sectional view taken along the line 33 of Fi 2 as indicated by the arrows;

Fig. 4 is a detail view; I

Fig. 5 is a partially broken away front view of another form of my propeller and 40 Fig. 6 is a cross sectionalview taken along the line 6-6 of Fig. 5 as indicated by the arrows.

Referring to the drawing, and particularly to Figs. 1 to 4 thereof. each blade B of my propeller comprises a main section 1 and a tip section 8 5 as shown. The main sections I of the blades B are mounted in a hub 9 of conventional design and are fixed therein so as to be fixed in pitch.

The tip section 8 is mounted'on the main section I of the blade B so as to be shiftable relative 5 thereto to vary the pitch of the tip section 8 independently of the fixed pitch at which the main section I is set. To this end a shaft Ill, disposed longitudinally of the blade B, is received in its outer portion in a suitable axial aperture in the tip section 8 and is fixedly secured therein by suitable means such as the pin I I. The portion of the shaft l0 not 'within the limits of the tip section 8 projects axially of the blade B toward the hub 9 to be received within the main section 1 of the blade B as will be 5 described.

A sleeve i 2 having both inwardly and outwardly radially projecting annular flanges I201. and I 2b at its'outer end is disposed in a suitable outwardly opening axial aperture in the outer end 10 portion of the main section I of the blade B. The sleeve I2 is secured in the above described position by suitable means such as screws l3 projecting through apertured portions of the flange in into the material of the main section 1. The in- Wardly projecting flange I22) is ofsuch width that the inwardly facing periphery thereof is of a diameter suited for a bearing in which the shaft l0 may be journaled. The portion of the shaft l8 projecting from the tip section 8 of I the blade B is disposed inside the sleeve l2 in .journaled relation with the inwardly projecting manner of a bearing. The inner sleeve I4 is restrained from rotation relativeto the sleeve l2 and the main section I of the blade B by means of a key l5.

The shaft Ill, in the portion thereof disposed within the inner sleeve I4, is provided with a helical groove Illa as shown. The inner sleeve l4 carries a rigidly mounted pin 16 projecting into the groove "la.

The innermost portion of the shaft is provided 5 with a collar l'l secured thereto by suitable means such as the setscrew l8. The outer periphery of the collar i1 is preferably of a diameter which fits the interior periphery of the sleeve l2 with only suificient clearance to permit rotational and 40 longitudinal sliding movement of the collar l'l within the sleeve 12. A helical compression spring l9, coiled aboutthe shaft ill, bears at its respective ends against the collar l1 and the inner end of the inner sleeve 14 to resiliently urge the shaft i8 and the tip section 8 of the blade B toward the hub 9. Inward movement of the shaft l0 and tip section 8 responsive to the pressure of the spring I9 is, of course, limited by engagement of the inner end of the tip section 8 with 5 the flanged outer end of the sleeve l2.

In operation of the above described. propeller, centrifugal force tends to act on the mass of the tip section 8 and the shaft ID to project the same radially outwardly. However, such outward projection is yieldingly resisted by the spring l9. As the speed of rotation of the propeller increases, the centrifugal force will increase and the tip section 8 and shaft ill will be moved outwardly to a point where the spring. I9 is sufficiently compressed toexert a force equal to the effect of centrifugal force on the mass of the tip section 8 and the shaft I0. It is then apparent that the tip section 8 and the shaft ID will move outl0 wardly and inwardly responsive to respective increase and decrease in the rotational speed of the propeller. As the shaft l0 moves outwardly and inwardly it is forced by the combination of the helical groove lfla. therein and the pin IE to rotate through an angle determined by the pitch of the helical groove Illa and the distance of outward or inward movement. Such rotation of the shaft ll] of course is accompanied by change in the pitch of the tip section 8 of the blade B. Thus the pitch of the tip section 8 varies in response to variation in the rotational speed of the propeller. The propeller may obviously be constructed for either increase or decrease of tip section pitch responsive to increase in speed by making the helical groove wind respectively right handed or left handed. Also the propeller may be readily arranged so that the tip section will reach a position normal to the plane of rotation of the propeller or even reach a position of re- 'verse pitch.

My propeller is, of course, well adapted for use either as a power driven propeller for creating movement of a fluid or as a power producing propeller to be rotated by a moving body of fluid directed thereagainst. However, my intended use of the propeller is in wind electric plants wherein my automatic blade tip pitch varying feature serves to regulate the speed of rotation of the propeller as the velocity of the wind to which it is subjected varies. For such use the helical groove lfla is made right-handed. as shown, so that the tip section pitch will increase with propeller speed and the parts of the propeller are so proportioned that the tip section pitch can increase to such an extent that the tip section 8 can reach a position normal to the plane of rotation of the propeller. The tip section 8 is of relatively small area compared to the area of the main section I of the blade B but, since it moves at a much greater linear velocity than portions of the blade B closer to the hub, it has a strong controlling effect on the characteristics of the propeller as to the ratio between wind velocity and propeller speed. As the wind velocity increases and the propeller speed tends to increase accordingly, the pitch of the tip section 8 increases to reduce the effectiveness of the wind in rotating the propeller and thus prevents the propeller speed from increasing as much as it would if the entire blade of the propeller were fixed in pitch. Further in creases in wind velocity accompanied by moderate increases in propeller speed finally cause the tip section 8 to assume a position normal to the plane of rotation of the propeller. In such position the tip sections 8 operate much in the manner of centrifugal blower vanes so as to place a substantial mechanical load on the propeller and to greatly increase the blade tip losses relative to the blade tip losses of a propeller wherein the entire blade is fixed in pitch. The result, of course, is

that the propeller speed will vary through a reasonably narrow range when the wind velocity varies through a very wide range and will have a very much lower maximum speed than a propeller wherein the entire blade is fixed in pitch.

The form of my propeller shown in Figs. 5 and 6 is generally similar to the above described form but differs therefrom in details as will be described. The main section 29 and tip section 2| of the blade C are similar to the main section I and tip section 8 of the blade B. The tip section 2| carries a shaft 22 anchored therein by a pin 23 in the same manner as the shaft II was anchored in the tip section 8 of the first form.

A sleeve 24 is disposed in a suitable outwardly opening axial recess in the outer end portion of the main section 20 of the blade C and is retained therein by the flange 25a of a flanged bearing element 25 secured to the outer end of the main section 20. The bearing element 25 projects inwardly into the outer end of the sleeve 24 and a pin 26 projects through the wall of the sleeve 24 into the bearing element 25 to prevent rotation of the sleeve 24 relative to the bearing element 25. The shaft 22 is journaled at one point in the bearing element 25 and at the inner end of the sleeve 24 is supported by a suitable bearing such as the ball bearing 21. A collar 28 is mounted on the shaft 22 just inwardly of thevbearing element 25 and is secured to the shaft 22 by means of a pin 28a so as to prevent longitudinally outward movement of the shaft 22.

The inner end of the shaft 22 is provided with a left-handed helical groove 22a. A sleeve 29 comprising an annular weight is mounted loosely on the inner end portion of the shaft 22 so as to be longitudinally slidablerelative to the shaft 22 and the sleeve 24. The weight 29 carries a Woodrufi key in a recess in its inner periphery, this key being engaged in the helical groove 22a of the shaft 22. The weight 29 also has a longitudinal keyway 29a in its exterior periphery in which is engaged a Woodrufi key 3| carried in a recess in the inner periphery of the sleeve 24.

The key 3| mounted in the sleeve 24 and engaged in the longitudinal keyway of the weight 29 prevents rotation of the weight 29 relative to the sleeve 24 and hence limits the weight 29 to longitudinal movement relative to the sleeve 24. The key 30 carried by the weight 29 and working in the helical groove 22a of the shaft 22 brings about rotation of the shaft 22 in response to longitudinal movement of the weight 29.

A helical compression spring 32, mounted on the shaft 22 in encircling relation thereto, bears at its respective ends against the collar 28 and the weight 29 so as to yieldingly resist outward movement of the weight 29.

In operation of the propeller centrifugal force tends to throw the weight 29 outwardly against the pressure of the spring 32. At any given rotational speed of the propeller the weight 29 will be disposed in an outwardly moved position wherein the spring 32 will be sufliciently compressed to exert a pressure equal to the effect of centrifugal force on the weight 29. Increase and decrease in the rotational speed will obviously cause the weight to be displaced respectively outwardly and inwardly. As the weight 29 moves outwardly and inwardly the shaft 22 will be rotated to alter the pitch of the tip section 2| of the blade C. Thus the pitch of the tip section 2| is varied responsive to variation in the rotational speed of the propeller. With the helical groove 22a of the shaft 22 extending in the manher of a left hand screw thread, as shown. the pitch of the tip section 2| will be increased responsive to increase in the rotational speed of the propeller. The effect of this pitch variation in controlling the speed at which the propeller will fords the advantages of variable pitch operation.

The great eifectiveness of a relatively small blade area, such as that of the tip section of my propeller, varied through a wide range of pitch and situated at a'considerable radius from themepeller hub enables effective speed control and yet requires only very light, compact and inexpensive pitch varying mechanism.

Commercial units embodying my invention in both of the forms disclosed have been built and operated and. have been found highly satisfactory in practical use.

It is apparent that I have invented a novel,

7 simple, light, compact, reliable, effective and inexpensive form of propeller automatically controlled through variation in the pitch of the tip sections of the blades thereof.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts .without departing from the scope of my invention.

What is claimed is:

1. A propeller having a hub and at least one blade mounted thereon in generally radial relation thereto, the main portion of said blade be- 5 ingfixed in pitch, the tip portion of said blade being divided from said main portion, a shaft element connecting said tip portion to said main portion, said shaft element having one portion fixed in one of said blade portions and a helically 4o grooved second portion joumaled in the other of said blade portions, 9. guide element fixed in said other'bla'de portion and engaged in said helical groove, said shaft and said guide element being so constructed and arranged that centrifugal 4 force created by rotation of said propeller and acting on the mass of said tip portion will cause outward movement of said tip portion accompanied by rotation thereof to vary the pitch thereof, and resilient means yieldingly' resisting outward movement of said tip portion.

2. A propeller having a hub and at least one ranged that centrifugal force' acting on the mass of said tip portion and saidshaft responsive to rotation of said propeller will cause radial movement and change of pitch of said tip portion in response to change'in the speed of rotation of said propeller.

3. A propeller having a hub and at least one propeller blade mounted in and projecting outwardly thereof, said blade being divided into respective main and tip portions of which said main portion is fixed in pitch, a shaft on said tip portion, a bearing in the outer part of said main portion wherein said shaft is journailed and inwardly of which said shaft projects, the Journailed portion of said shaft having .a helical groove therein, an element fixed in said bearing I and engaged in said groove. said shaft, bearing,

- groove and element being so constructed and arranged that outward movement of said tippertion and said shaft responsive to centrifugal force created by. rotation of said propeller will be accompanied by rotation altering the pitch of said tip portion,.a collar mounted on the inner portion of said shaft, and a helical compression spring disposed co-axially on said shaft and, at its respective ends, abutting said bearing and said collar to yieldingly resist outward displacement of said shaft and said tip portion.

JOSEPH H. JACOBS. 

